ORIGIN AND SIGNIFICANCE OF CORN BELT MAIZE 



145 



efficient between yield and index differences is r = +.40, a significant value 

 statistically. 



In terms of practical corn breeding, the distribution of single crosses in 

 Figures 8.6 and cS.7 is of particular significance. If these observations are 

 critical (we have produced a repea table result) it means that one could have 

 eliminated from the testing program the lower one-third of the crosses on the 

 basis of index differences, without losing any of the top 10 per cent of the 

 highest yielding hybrids. In the case of the 100 hybrids in Figure 8.7, one could 

 have eliminated from testing 35 per cent of the crosses, thereby permitting the 

 inclusion of 35 additional hybrids in this particular testing area. If further 



1949 



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5 10 15 20 



INDEX DIFFERENCE 



25 



r= +.40 



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Fig. 8.7 — Scatter diagram depicting relationship between grain yields of 100 single cross 

 hybrids and morphological differences of inbred paren ts of the hybrids. Explanation in text . 



